<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <div id="app">
        <input type="text" v-model="n1" @input="dataChange">
        <select v-model="opt">
            <option value="+">+</option>
            <option value="-">-</option>
            <option value="*">*</option>
            <option value="/">/</option>
        </select>
        <input type="text" v-model="n2"  @input="dataChange">
        =
        <input type="text" v-model="result">

    </div>

</body>
<script src="./lib/vue-2.4.0.js"></script>
<script>
    const vm=new Vue({
        el:"#app",
        data:{
            n1:0,
            n2:0,
            opt:"+",
            result:0

        },
        methods:{
           dataChange(){
                this.result=parseInt(this.n1)+parseInt(this.n2)

            }

        }
    })
</script>
</html>
